Force sensor

ABSTRACT

A force sensor including a first surface and a second surface facing each other in a first direction; a first protrusion protruded from the first surface toward the second surface; a first electrode on the first protrusion; a first force sensing layer on the first electrode; a second protrusion protruded from the second surface toward the first surface; and a second electrode on the second protrusion, wherein the first protrusion and the second protrusion are not overlapped with each other or are partially overlapped with each other.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119 to Korean PatentApplication No. 10-2018-0039899, filed on Apr. 5, 2018 in the KoreanIntellectual Property Office, the disclosure of which is incorporated byreference herein in its entirety.

1. TECHNICAL FIELD

The present invention relates to a force sensor, and more particularly,to a force sensor for sensing a shear force.

2. DESCRIPTION OF THE RELATED ART

Electronic devices that provide images to a user such as a smart phone,a tablet personal computer (PC), a digital camera, a laptop computer, anavigation device and a smart television include a display device fordisplaying images. Such a display device includes a display panel forgenerating and displaying an image and various input devices.

A touch panel that recognizes a touch input is widely employed as adisplay device of a smartphone or a tablet PC. Due to its convenience, atouch panel is increasingly used as a replacement for existing physicalinput devices such as a keypad.

A force sensor may be used on a display device employing a touch panel.Typically, a force sensor detects a force applied in the thicknessdirection of the display device. Although user interfaces (UIs) may onlybe implemented with inputs in the thickness direction of the displaypanel, to realize a more diverse and realistic UI, it may be useful torecognize forces applied in various directions as separate inputs.

SUMMARY

According to an exemplary embodiment of the present invention, there isprovided a force sensor. The force sensor comprises: a first surface anda second surface facing each other in a first direction; a firstprotrusion protruded from the first surface toward the second surface; afirst electrode on the first protrusion; a first force sensing layer onthe first electrode; a second protrusion protruded from the secondsurface toward the first surface; and a second electrode on the secondprotrusion, wherein the first protrusion and the second protrusion arenot overlapped with each other or are partially overlapped with eachother.

According to another exemplary embodiment of the present invention,there is provided a force sensor. The force sensor comprises: a firstsensor element comprising a first substrate, a first protrusion disposedon the first substrate, a first electrode on the first protrusion, and afirst force sensing layer on the first electrode; and a second sensorelement comprising a second substrate, a second protrusion disposed onthe second substrate, and a second electrode disposed on the secondprotrusion, wherein the force sensing layer faces the second electrode,and wherein the first protrusion and the second protrusion do notoverlap with each other, or at least partially overlap with each other.

According to another exemplary embodiment of the present invention,there is provided a force sensor. The force sensor comprises: aplurality of sensing cells; a plurality of first electrodes extended ina first extending direction; and a plurality of second electrodesextended in a second extending direction and intersecting with the firstelectrodes; wherein at least one of the sensing cells includes aplurality of sub-sensing regions located at intersections between thefirst electrodes and the second electrodes, wherein at least one of thesub-sensing regions comprises: a first surface and a second surfacefacing each other in a thickness direction of the force sensor, aplurality of protrusions protruded from the first surface toward thesecond surface, one of the first electrodes on the plurality of firstprotrusions, and a first force sensing layer on the one first electrode,a plurality of second protrusions protruded from the second surfacetoward the first surface, and one of the second electrodes on theplurality of second protrusions, wherein an adjacent first protrusionand second protrusion form a pair of protrusions, and wherein the firstprotrusion and the second protrusion in the pair do not overlap witheach other, or at least partially overlap with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will become moreapparent by describing in detail exemplary embodiments thereof withreference to the attached drawings, in which:

FIG. 1 illustrates cross-sectional views of a pressure sensor accordingto an exemplary embodiment of the present invention;

FIG. 2 is a graph illustrating electrical resistance verses force of afirst force sensing layer according to an exemplary embodiment of thepresent invention;

FIG. 3 illustrates cross-sectional views of a pressure sensor accordingto another exemplary embodiment of the present invention;

FIG. 4 illustrates cross-sectional views of a pressure sensor accordingto yet another exemplary embodiment of the present invention;

FIG. 5 is a cross-sectional view of a force sensor according to yetanother exemplary embodiment of the present invention;

FIG. 6 is cross-sectional view of a force sensor according to yetanother exemplary embodiment of the present invention;

FIG. 7 is cross-sectional view of a force sensor according to yetanother exemplary embodiment of the present invention;

FIG. 8 is cross-sectional view of a force sensor according to yetanother exemplary embodiment of the present invention;

FIG. 9 is a cross-sectional view of a force sensor according to yetanother exemplary embodiment of the present invention;

FIG. 10 is cross-sectional view of a force sensor according to yetanother exemplary embodiment of the present invention;

FIG. 11 is a plan view showing the layout of a force sensor according toan exemplary embodiment of the present invention when viewed from above.

FIG. 12 is an enlarged view of one of a plurality of sensing cells ofFIG. 11, according to an exemplary embodiment of the present invention;

FIG. 13 is a plan view showing the layout of a first sensor element ofFIG. 12, according to an exemplary embodiment of the present invention;

FIG. 14 is a plan view showing the layout of a second sensor element ofFIG. 12, according to an exemplary embodiment of the present invention;

FIG. 15 is a cross-sectional view taken along line XV-XV′ shown in FIG.12, according to an exemplary embodiment of the present invention;

FIG. 16 is a flowchart for illustrating a method for sensing a shearforce and utilizing information by a pressure sensor according to anexemplary embodiment of the present invention;

FIG. 17 is a plan view showing a method of detecting a sensing signalwhen a rightward shearing force is received, according to an exemplaryembodiment of the present invention;

FIG. 18 is a plan view showing a method of detecting a sensing signalwhen a leftward shearing force is received, according to an exemplaryembodiment of the present invention;

FIG. 19 is a plan view showing a method of detecting a sensing signalwhen a downward shearing force is received, according to an exemplaryembodiment of the present invention;

FIG. 20 is a plan view showing a method of detecting a sensing signalwhen an upward shearing force is received, according to an exemplaryembodiment of the present invention;

FIG. 21 is a plan view showing the layout of a first sensor element of aforce sensor according to another exemplary embodiment of the presentinvention;

FIG. 22 is a plan view showing the layout of a force sensor according toyet another exemplary embodiment of the present invention;

FIG. 23 is a cross-sectional view taken along line XXIII-XXIII′ of FIG.22, according to an exemplary embodiment of the present invention;

FIG. 24 is a plan view showing the layout of a force sensor according toyet another exemplary embodiment of the present invention;

FIGS. 25, 26 and 27 are plan views showing the layouts of a force sensoraccording to a variety of exemplary embodiments of the presentinvention; and

FIGS. 28 and 29 are views of electronic devices including pressuresensors according to exemplary embodiments of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Exemplary embodiments of the present invention will be described morefully hereinafter with reference to the accompanying drawings. Theinventive concept may, however, be embodied in many different forms andshould not be construed as being limited to the embodiments set forthherein. Like reference numerals may refer to like elements throughoutthe specification.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise.

It will be understood that when an element or layer is referred to asbeing “on”, “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present.

In the drawings, components may be exaggerated or reduced in size forconvenience of explanation.

A force sensor according to exemplary embodiments of the presentinvention includes a first electrode, a second electrode, and at leastone force sensing layer. The first electrode and the second electrodemay be separated from each other. One of the first electrode and thesecond electrode may be a driving electrode and the other may be asensing electrode. The first electrode and the second electrode may notbe in direct contact with each other. In a certain state, e.g., when theforce sensor is pressed, the first electrode and the second electrodemay get closer to each other, with the force sensing layer therebetween.When this happens, one surface of the force sensing layer comes intocontact with the first electrode, and the other surface of the forcesensing layer comes into contact with the second electrode, such that acurrent can flow between the first electrode and the second electrodethrough the force sensing layer.

FIG. 1 illustrates cross-sectional views of a force sensor according toan exemplary embodiment of the present invention. FIG. 1(a) shows aforce sensor when it is not pressed; FIG. 1(b) shows the force sensorwhen it is pressed in a thickness direction; and FIG. 1(c) shows theforce sensor when it is pressed in the thickness direction as well as ina horizontal direction.

Referring to FIG. 1(a), the force sensor 1 includes a first sensorelement 10 and a second sensor element 20 facing each other. Each of thefirst sensor element 10 and the second sensor element 20 may be, but isnot limited to, a film, a sheet, a plate, a panel or a stacked layer.

The first sensor element 10 and the second sensor element 20 may bespaced apart from each other in thickness directions Z1 and Z2. Asupporter 30 may be disposed between the first sensor element 10 and thesecond sensor element 20 to maintain the spacing therebetween. Thesupporter 30 may be disposed on side portions of the first sensorelement 10 and the second sensor element 20. The supporter 30 may bedisposed along edges of the first sensor element 10 and the secondsensor element 20 when viewed from above. A variety of layouts andshapes of the supporter 30 will be described later with reference toFIGS. 25 to 27.

The first sensor element 10 includes a first substrate 11, a firstprotrusion 12 disposed on the first substrate 11, a first electrode 13disposed on the first protrusion 12, and a first force sensing layer 14disposed on the first electrode 13. The second sensor element 20includes a second substrate 21, a second protrusion 22 disposed on thesecond substrate 21, and a second electrode 23 disposed on the secondprotrusion 22.

The first substrate 11 and the second substrate 21 face each other. Inthe following description, the surfaces of the substrates 11 and 21 thatface each other may be referred to as first surfaces, and the opposingsurfaces of the substrates 11 and 21 may be referred to as secondsurfaces. The first protrusion 12 is disposed on the first surface ofthe first substrate 11, and the second protrusion 22 is disposed on thefirst surface of the second substrate 21.

A force or pressure may be input to the force sensor 1 through thesecond surface of the second substrate 21, as shown in the drawings. Itis to be understood, however, that the present invention is not limitedthereto. A force or pressure may be input either through the secondsurface of the first substrate 11 or through the second surface of thefirst substrate 11 as well as the second surface of the second substrate21.

Each of the first substrate 11 and the second substrate 21 may include amaterial such as polyethylene, polyimide, polycarbonate, polysulfone,polyacrylate, polystyrene, polyvinyl chloride, polyvinyl alcohol,poly(norbornene), and poly ester. According to an exemplary embodimentof the present invention, each of the first substrate 11 and the secondsubstrate 21 may be formed as a polyethylene terephthalate (PET) film ora polyimide film. It is to be understood, however, that the presentinvention is not limited thereto. Each of the first substrate 11 and thesecond substrate 21 may be made of glass, quartz, etc., or may be madeof an insulating layer such as an organic insulating layer or aninorganic insulating layer.

The first protrusion 12 is disposed such that it protrudes from thefirst substrate 11 in the thickness direction Z1. The first protrusion12 may protrude from the first surface of the first substrate 11 in afirst thickness direction Z1. The first thickness direction Z1 isindicated by the arrow pointed toward the second substrate 21.

The second protrusion 22 is disposed such that it protrudes from thesecond substrate 21 in the thickness direction Z2. The second protrusion22 may protrude from the first surface of the second substrate 21 in asecond thickness direction Z2. The second thickness direction Z2 isindicated by the arrow pointed toward the first substrate 11.

The first protrusion 12 and the second protrusion 22 may be made of aninsulating material. The first protrusion 12 and the second protrusion22 may be made of an organic material or an inorganic material. Forexample, the first protrusion 12 and the second protrusion 22 may bemade of a polyacrylic resin, a polyacrylate resin, a polyimide resin, orthe like, or may be made of a silicone compound.

In exemplary embodiments of the present invention, the first protrusion12 and the second protrusion 22 may be made of a material havingelasticity. When the first protrusion 12 and the second protrusion 22have a certain elasticity, they can absorb some of an externally appliedforce, such as a force in the thickness directions Z1 and Z2 or a shearforce, to prevent damage to the elements of the force sensor 1. Further,each of the first and second protrusions 12 and 22 can be restored toits original shape after deformation by the force.

The first protrusion 12 and the second protrusion 22 may have, but arenot limited to, a dome shape, a pyramid-like square pillar shape, acylindrical shape, or the like. In the drawings, the first protrusion 12and the second protrusion 22 have a dome shape.

According to an exemplary embodiment of the present invention, the width(e.g., the diameter of the lower end) of the first protrusion 12 and thesecond protrusion 22 may range from 100 μm to 500 μm. The height of eachof the first protrusion 12 and the second protrusion 22 may range from100 μm to 500 μm.

The first protrusion 12 and the second protrusion 22 may havesubstantially the same shape and size.

The first protrusion 12 and the second protrusion 22 may be disposedsuch that they do not overlap with each other at least partially in thethickness directions Z1 and Z2. In other words, the first protrusion 12and the second protrusion 22 may be staggered when viewed from above.The first protrusion 12 and the second protrusion 22, which arestaggered, form a pair of protrusions. Although FIG. 1 shows only onepair of protrusions, two or more pairs of protrusions may be provided.

The center 12 c of the first protrusion 12 may be spaced apart from thecenter 22 c of the second protrusion 22 by a certain distance p in thehorizontal directions X1 and X2. For example, the center 12 c of thefirst protrusion 12 may be spaced apart from the center 22 c of thesecond protrusion 22 in a first linear direction X1, and the center 22 cof the second protrusion 22 may be spaced apart from the center 12 c ofthe first protrusion 12 in a second linear direction X2 opposite to thefirst linear direction X1.

It is to be noted that if the first protrusion 12 is spaced apart fromthe second protrusion 22 too far in the horizontal directions X1 and X2,the first protrusion 12 and the second protrusion 22 might not come intotight contact with each other by a shearing force. Accordingly, thedistance d lies within a predetermined range. For example, the distancep between the center 12 c of the first protrusion 12 and the center 22 cof the second protrusion 22 in the first linear direction X1 may besmaller than the sum of the width of the first protrusion 12 and thewidth of the second protrusion 22.

The center 12 c of the first protrusion 12 and the center 22 c of thesecond protrusion 22 may refer to the center of the first protrusion 12in the width direction and the center of the second protrusion 22 in thewidth direction, respectively. The first protrusion 12 and the secondprotrusion 22 may have the maximum protrusion height at their centers 12c and 22 c, respectively.

FIG. 1(a) shows an example where the first protrusion 12 and the secondprotrusion 22 do not overlap with each other at all in the thicknessdirections Z1 and Z2.

The side of the first protrusion 12 and the second protrusion 22indicated by the arrow X1 (e.g., the right side in FIG. 1) may be a“first side”, and the opposing side indicated by the arrow X2 (e.g., theleft side in FIG. 1) may be a “second side”. If the first protrusion 12does not overlap with the second protrusion 22 at all, the side surfaceof the first protrusion 12 on the second side does not overlap with thesecond protrusion 22, and the side surface of the second protrusion 22on the first side does not overlap with the first protrusion 12. Theterms “the side surface on the first side” and “the side surface on thesecond side” may refer to the outermost side surfaces in the respectivedirections, for example, the side surfaces near the lower end of thedome-like protrusion. A horizontal distance d between the side surface12 b on the second side of the first protrusion 12 and the side surface22 a on the first side of the second protrusion 22 may be smaller thanthe width of the first protrusion 12 (or the second protrusion 22) andmay be equal to or less than half the width of the first protrusion 12(or the second protrusion 22). In the drawings, the first protrusion 12has the side surface on the first side 12 a, and the second protrusion22 has the side surface on the second side 22 b. The side surface on thefirst side 12 a is opposite the side surface 12 b on the second side ofthe first protrusion 12. The side surface on the second side 22 b isopposite the side surface 22 a on the first side of the secondprotrusion 22.

The first electrode 13 is disposed on the first protrusion 12. The firstelectrode 13 covers the first protrusion 12 and extends from one side ofthe first protrusion 12 to the first surface of the first substrate 11on which the first protrusion 12 is not disposed. The first electrode 13is not disposed in a region on the first surface of the first substrate11 including the area facing the center 22 c of the second protrusion22. The region where the first electrode 13 is not disposed is a firstopening area OP1. In the first opening area OP1, the first surface ofthe first substrate 11 is exposed without being covered by the firstelectrode 13. The first opening area OP1 overlaps with the center 22 cof the second protrusion 22 that it faces. Furthermore, the firstopening area OP1 may overlap with the entire second protrusion 22. Thewidth of the first opening area OP1 may be equal to or greater than thewidth of the second protrusion 22. According to an exemplary embodimentof the present invention, the width of the first opening area OP1 may beone to four times the width of the second protrusion 22, for example,approximately two times.

The second electrode 23 is disposed on the second protrusion 22. Thesecond electrode 23 covers the second protrusion 22 and extends from theside surface of the second protrusion 22 to the first surface of thesecond substrate 21 on which the second protrusion 22 is not disposed.The second electrode 23 is not disposed in a region on the first surfaceof the second substrate 21 including the area facing the center 12 c ofthe first protrusion 12. The region where the second electrode 23 is notdisposed is a second opening area OP2. In the second opening area OP2,the first surface of the second substrate 21 is exposed without beingcovered by the second electrode 23. The second opening area OP2 overlapswith the center 12 c of the first protrusion 12 that it faces.Furthermore, the second opening area OP2 may overlap with the entirefirst protrusion 12. The width of the second opening area OP2 may beequal to or greater than the width of the first protrusion 12. Accordingto an exemplary embodiment of the present invention, the width of thesecond opening area OP2 may be one to four times the width of the firstprotrusion 12, for example, approximately two times.

Each of the first opening area OP1 and the second opening area OP2 mayhave a circular shape, an elliptical shape, a rectangular shape, or thelike when viewed from above, as well as various other shapes. When thefirst and second opening areas OP1 and OP2 have an elongated shape inone direction, a longitudinal direction may be the same as theabove-described linear directions X1 and X2.

A part of the first opening area OP1 on the second side of the firstprotrusion 12 and a part of the second opening area OP2 on the firstside of the second protrusion 22 may overlap in the thickness directionsZ1 and Z2.

Each of the first electrode 13 and the second electrode 23 may include aconductive material such as silver (Ag) and copper (Cu). The firstelectrode 13 and the second electrode 23 may be formed, for example, byscreen printing. In some exemplary embodiments of the present invention,the first electrode 13 and the second electrode 23 may be made of atransparent, conductive oxide layer such as ITO and IZO, or atransparent, conductive material such as a nanowire, a carbon nanotubeand a conductive polymer.

Thicknesses of the first electrode 13 and the second electrode 23 maybe, but are not limited to, 2 μm to 8 μm, or approximately 4 μm.

The first force sensing layer 14 is disposed on the first electrode 13.The first force sensing layer 14 may have substantially the same patternshape as the first electrode 13. The first surface of the firstsubstrate 11 may be exposed without being covered by the first forcesensing layer 14 in the first opening area OP1.

The first force sensing layer 14 may comprise a pressure sensitivematerial. The pressure sensitive material may include metalnanoparticles such as nickel, aluminum, tin, copper, or carbon. Thepressure sensitive material may be dispersed in a polymer resin in theform of particles. It is to be understood, however, that the presentinvention is not limited thereto.

The first force sensing layer 14 may be thicker than the first electrode13. The thickness of the first force sensing layer 14 may range from 4μm to 12 μm, e.g., approximately 8 μm.

FIG. 2 is a graph illustrating electrical resistance verses force of thefirst force sensing layer according to an exemplary embodiment of thepresent invention.

Referring to FIG. 2, as the force applied to the first force sensinglayer 14 increases, the electrical resistance decreases. By using thischaracteristic, it is possible to sense whether a force is applied andthe magnitude of the applied force.

For example, assume that a driving voltage is applied to the firstelectrode 13 and a current amount or voltage flowing in the secondelectrode 23 is sensed. When the force sensor 1 is not pressed as shownin FIG. 1(a), no current flows from the first electrode 13 to the secondelectrode 23 because the first electrode 13 and the second electrode 23are spaced apart from each other. In other words, they are electricallydisconnected from each other.

As shown in FIG. 1(b), if a force is applied in the second thicknessdirection Z2 from the second surface of the second substrate 21, thedistance between the first substrate 11 and the second substrate 21 isreduced. In this case, the first force sensing layer 14 disposed on thepart of the first electrode 13 on the first protrusion 12 is broughtinto contact with the first surface of the second substrate 21 exposedvia the second opening area OP2. In addition, the part of the secondelectrode 23 on the second protrusion 22 may be brought into contactwith the first surface of the first substrate 11 exposed via the firstopening area OP1. As the force in the second thickness direction Z2increases, the force transmitted to the first force sensing layer 14 mayincrease while the resistance of the first force sensing layer 14 maydecrease. Since the first force sensing layer 14 is in contact with thefirst surface of the second substrate 21 in the second opening area OP2,but is electrically disconnected from the second electrode 23, nocurrent flows in the second electrode 23 even, e.g., if a drivingvoltage is applied to the first electrode 13.

As shown in FIG. 1(c), when a force in the second thickness direction Z2and a force in the first linear direction X1 (e.g., a shearing force),which is the horizontal direction, are applied simultaneously, thesecond protrusion 22 moves, e.g., down and across. If a force (e.g., ashearing force) equal to or greater than a threshold value is applied,the second electrode 23 on the second protrusion 22 comes in contactwith the first force sensing layer 14 disposed on the first electrode 13on the first protrusion 12. When the shear force is relative weak andthe force transmitted to the first force sensing layer 14 is small, theresistance of the first force sensing layer 14 is high, such thatcurrent hardly flows to the second electrode 23. On the other hand, whenthe shear force is strong and the force applied to the first forcesensing layer 14 is increased, the resistance of the first force sensinglayer 14 is low, such that a current flows from the first electrode 13to the second electrode 23 through the first force sensing layer 14.Therefore, it is possible to determine whether there is a shear force inthe first linear direction X1 and, if there is a shear force, to sensethe magnitude thereof, by checking the amount of current or voltagesensed by the second electrode 23.

In contrast to the example shown, when a force is applied in the secondlinear direction X2, the distance p between the center 12 c of the firstprotrusion 12 and the center 22 c of the second protrusion 22 isincreased. Therefore, the first electrode 13 and the second electrode 23do not come in contact with each other with the first force sensinglayer 14 therebetween, such that no sensing current would be detected atthe second electrode 23. To sense the shear force in the second lineardirection X2, the positions of the first protrusion 12 and the secondprotrusion 22 may be reversed in the horizontal directions X1 and X2.Examples of how to detect and sense a shear force in various directionsby re-arranging the first and second protrusions 12 and 22 will bedescribed in detail below with reference to FIG. 11.

FIG. 3 illustrates cross-sectional views of a force sensor according toanother exemplary embodiment of the present invention. FIG. 3(a) shows aforce sensor when it is not pressed; FIG. 3(b) shows the force sensor 1when it is pressed in the thickness directions Z1 and Z2; and FIG. 3(c)shows the force sensor when it is pressed in the thickness directions Z1and Z2 as well as in the horizontal direction.

FIG. 3(a) shows an example where the first protrusion 12 and the secondprotrusion 22 overlap with each other partially in the thicknessdirections Z1 and Z2.

Referring to FIG. 3(a), when a force sensor 1_1 is not pressed, thefirst protrusion 12 and the second protrusion 22 partially overlap witheach other.

For example, the side surface 12 b on the second side of the firstprotrusion 12 overlaps with the second protrusion 22, and the sidesurface 22 a on the first side of the second protrusion 22 overlaps withthe first protrusion 12. The portion of the second protrusion 22overlapping with the side surface 12 b of the first protrusion 12 mayextend from the center 22 c of the second protrusion 22 to the firstside of the second protrusion 22 (in the first linear direction X1). Theportion of the first protrusion 12 overlapping with the side surface 22a of the second protrusion 22 may extend from the center 12 c of thefirst protrusion 12 to the second side of the first protrusion 12 (inthe second linear direction X2). The width in the horizontal directionin which the first protrusion 12 and the second protrusion 22 overlapwith each other may be smaller than half the width of the firstprotrusion 12 (or the second protrusion 22). In an exemplary embodimentof the present invention, the side surface 22 a of the second protrusion22 and the side surface 12 b of the first protrusion 12 overlap in thethickness directions Z1 and Z2 and may be aligned with each other.

As shown in FIG. 3(b), if a force is applied in the second thicknessdirection Z2 from the second surface of the second substrate 21, thedistance between the first substrate 11 and the second substrate 21 isreduced. In this case, the first force sensing layer 14 disposed on thepart of the first electrode 13 on the first protrusion 12 is broughtinto contact with the first surface of the second substrate 21 exposedvia the second opening area OP2, and the part of the second electrode 23on the second protrusion 22 may be brought into contact with the firstsurface of the first substrate 11 exposed via the first opening areaOP1. When this happens, the part of the second electrode 23 disposed onthe side of the second protrusion 22 (e.g., the portion extended in thefirst linear direction X1 from the center 22 c) may come in contact withthe part of the first force sensing layer 14 disposed on the firstelectrode 13 on the side of the first protrusion 12 (e.g., the portionextended in the second linear direction X2 from the center 12 c).However, since the parts of the first and second electrodes 13 and 23come in contact with each other at an inclined angle, the first forcesensing layer 14 does not receive a sufficient force, and thus, theresistance of the first force sensing layer 14 is high. Accordingly, nocurrent or a small amount of current flows to the second electrode 23.

In FIG. 3(b), when the first substrate 11 and the second substrate 21approach to each other, if the force sensor 1_1 is further pressed inthe thickness direction Z2 even after the first protrusion 12 and thesecond protrusion 22 overlapping with each other have been pressed, thesecond protrusion 22 of the second substrate 21 may be shifted towardthe second side of the second protrusion 22. Accordingly, as shown inFIG. 3(b), the second substrate 21 may be slightly shifted to the leftrelative to the first substrate 11.

As shown in FIG. 3(c), when a force in the second thickness direction Z2and a force in the first linear direction X1 (e.g., a shearing force),which is the horizontal direction, are applied simultaneously, thesecond protrusion 22 moves, e.g., down. Then, the second electrode 23 onthe second protrusion 22 comes into tight contact with the first forcesensing layer 14 disposed on the first electrode 13 on the firstprotrusion 12. As a shear force is increased, the force applied to thefirst force sensing layer 14 is increased, and accordingly, theresistance of the first force sensing layer 14 is lowered so that acurrent may flow from the first electrode 13 toward the second electrode23 through the first force sensing layer 14. The amount of current orvoltage flowing to the second electrode 23 in the state shown in FIG.3(c) is different from the amount of current or voltage flowing to thesecond electrode 23 in the state shown in FIG. 3(b). Therefore, it ispossible to determine whether or not the shear force is applied bychecking the amount of current or voltage and, if the shear force isapplied, to sense the magnitude thereof.

FIG. 4 illustrates cross-sectional views of a force sensor according toyet another exemplary embodiment of the present invention. FIG. 4(a)shows a force sensor 1_2 when it is not pressed, and FIG. 4(b) shows theforce sensor 1_2 when it is pressed in the horizontal direction. FIG. 4illustrates an example where the spacing between the first substrate 11and the second substrate 21 is already narrow in the thicknessdirections Z1 and Z2 when the force sensor 1_2 is not pressed.

Referring to FIG. 4(a), when the force sensor 12 is not pressed, thefirst force sensing layer 14 disposed on the first electrode 13 on thefirst protrusion 12 comes in contact with the first surface of thesecond substrate 21 exposed through the second opening area OP2. Inaddition, the second electrode 23 on the second protrusion 22 comes incontact with the first surface of the first substrate 11 exposed throughthe first opening area OP1. The second electrode 23 disposed on thefirst side of the second protrusion 22 may come in contact the firstforce sensing layer 14 disposed on the first electrode 13 on the secondside of the first protrusion 12. However, since they come in contactwith each other at an inclined angle, the first force sensing layer 14does not receive a sufficient force, and thus, the resistance of thefirst force sensing layer 14 is high, so no current or a small amount ofcurrent flows to the second electrode 23.

As shown in FIG. 4(b), when a force in the first linear direction X1(e.g., a shearing force), which is the horizontal direction, is applied,the second protrusion 22 moves in one direction, e.g., to the right.Then, the second electrode 23 on the second protrusion 22 comes intotight contact with the first force sensing layer 14 disposed on thefirst electrode 13 on the first protrusion 12. As a shear force isincreased, the force applied to the first force sensing layer 14 isincreased, and accordingly, the resistance of the first force sensinglayer 14 is lowered so that a current may flow from the first electrode13 toward the second electrode 23 through the first force sensing layer14. Thus, it is possible to determine whether or not the shear force isapplied and, if the shear force is applied, to sense the magnitudethereof.

Hereinafter, a variety of force sensors according to exemplaryembodiments of the present invention will be described.

FIG. 5 is a cross-sectional view of a force sensor according to anotherexemplary embodiment of the present invention.

A force sensor 1_3 according to the exemplary embodiment shown in FIG. 5is substantially identical to the force sensor 1 shown in FIG. 1 exceptthat a second sensor element 20_3 also includes a force sensing layer.

For example, a second force sensing layer 24 is disposed on the secondelectrode 23 of the second sensor element 20_3 of the force sensor 1_3.The second force sensing layer 24 may have substantially the samepattern shape as the second electrode 23. The first surface of thesecond substrate 21 may be exposed without being covered by the secondforce sensing layer 24 in the second opening area OP2.

The second force sensing layer 24 may include a pressure sensitivematerial, like the first force sensing layer 14. The second forcesensing layer 24 may perform the same function as the first forcesensing layer 14.

According to the exemplary embodiment shown in FIG. 5, when the secondprotrusion 22 is moved toward the first protrusion 12 by a shear force,the second force sensing layer 24 disposed on the second electrode 23 onthe second protrusion 22 and the first force sensing layer 14 disposedon the first electrode 13 on the first protrusion 12 come in contactwith each other. The resistances of the first force sensing layer 14 andthe second force sensing layer 24 change according to the magnitude ofthe force transmitted to them. When the resistances of the first forcesensing layer 14 and the second force sensing layer 24 are lowered, acurrent may flow from the first electrode to the second electrode 23through the first force sensing layer 14 and the second force sensinglayer 24. Therefore, it is possible to determine whether there is ashear force in the first linear direction X1 and if there is the shearforce, to sense the magnitude thereof by checking the amount of currentor voltage sensed by the second electrode 23.

FIG. 6 is cross-sectional view of a force sensor according to yetanother exemplary embodiment of the present invention.

A force sensor 1_4 according to the exemplary embodiment shown in FIG. 6is substantially identical to the force sensor 1 shown in FIG. 1 exceptthat a first electrode 13_4, a first force sensing layer 14_4, and asecond electrode 23_4 are formed without a first opening area and asecond opening area. In addition, insulating layers 15 and 25 aredisposed at the positions of the first opening area and the secondopening area, respectively.

For example, the first electrode 13_4 of the first sensor element 10_4covers the first protrusion 12, and is extended from both sides of thefirst protrusion 12 to the first surface of the first substrate 11 wherethe first protrusion 12 is not disposed. The first electrode 13_4 isextended to a region facing the center 22 c of the second protrusion 22.The first electrode 13_4 may cover the entire first surface of the firstsubstrate 11. The first force sensing layer 14_4 is disposed on thefirst electrode 13_4. The first force sensing layer 14_4 may cover theentire surface of the first electrode 13_4. According to the presentembodiment, the first electrode 13_4 and the first force sensing layer14_4 are disposed in the region facing the center 22 c of the secondprotrusion 22, and thus, the first opening area OP1 such as one shown inFIG. 1 may not be provided.

The second electrode 23_4 of a second sensor element 20_4 covers thesecond protrusion 22 and extends from the side surfaces of the secondprotrusion 22 to the first surface of the second substrate 21 on whichthe second protrusion 22 is not disposed. The second electrode 23_4 isextended to a region facing the center 12 c of the first protrusion 12.The second electrode 23_4 may cover the entire first surface of thesecond substrate 21. According to the present embodiment, the secondelectrode 23_4 is disposed in the region facing the center 12 c of thefirst protrusion 12, and thus, the second opening area OP2 such as theone shown in FIG. 1 may not be formed.

The first insulating layer 15 may be disposed on the first force sensinglayer 14_4, and the second insulating layer 25 may be disposed on thesecond electrode 23_4.

The first insulating layer 15 is disposed in a region on the first forcesensing layer 14_4 including the area facing the center 22 c of thesecond protrusion 22. The first insulating layer 15 is disposed suchthat the first force sensing layer 14_4 disposed on the first electrode13_4 on the first protrusion 12 is exposed at least partially. The shapeof the first insulating layer 15 when viewed from above may besubstantially identical to the first opening area OP1 in FIG. 1.

The second insulating layer 25 is disposed in a region on the secondelectrode 23_4 including the area facing the center 12 c of the firstprotrusion 12. The second insulating layer 25 is disposed such that thesecond electrode 23_4 on the second protrusion 22 is exposed at leastpartially. The shape of the second insulating layer 25 when viewed fromabove may be substantially identical to the second opening area OP2 inFIG. 1.

According to this present embodiment, when the distance between thefirst substrate 11 and the second substrate 21 is reduced by pressing inthe thickness directions Z1 and Z2, the surface of the first forcesensing layer 14_4 disposed on the first electrode 13_4 on the firstprotrusion 12 may come into contact with the second insulating layer 25.In addition, the second electrode 23_4 on the second protrusion 22 maycome in contact with the first insulating layer 15. Therefore, when aforce is received in the thickness directions Z1 and Z2, the flow of thecurrent from the first electrode 13_4 to the second electrode 23_4 canbe effectively blocked by the first insulating layer 15 and the secondinsulating layer 25. As a consequence, noise in the sensing shear forcecan be prevented. On the other hand, when a force is received in thefirst linear direction X1, which is the horizontal direction, the firstforce sensing layer 14_4 may come into direct contact with the secondelectrode 23_4, so that a current may flow. Accordingly, it is possibleto determine whether there is a shear force and to sense its magnitude.

FIG. 7 is cross-sectional view of a force sensor according to yetanother exemplary embodiment of the present invention.

A force sensor 1_5 according to the exemplary embodiment shown in FIG. 7is substantially identical to the force sensor 1 shown in FIG. 1 exceptthat a first electrode 13_5 and a first force sensing layer 14_5 arepatterned so that the first protrusion 12 is exposed, and a secondelectrode 23_5 is patterned so that the second protrusion 22 is exposed.

For example, a first sensor element 10_5 includes a first protrusionopened portion EX1 that exposes the center 12 c of the first protrusion12, and a second sensor element 20_5 includes a second protrusion openedportion EX2 that exposes the center 22 c of the second protrusion 22.The first and second protrusion opened portions EX1 and EX2 expose thecenter 12 c of the first protrusion 12 and the center 22 c of the secondprotrusion 22 but not their peripheral portions.

Therefore, when the force sensor 1_5 receives a force in the thicknessdirections Z1 and Z2, even though the exposed top of the center 12 c ofthe first protrusion 12 comes into contact with the first surface of thesecond substrate 21, and the exposed top of the center 22 c of thesecond protrusion 22 comes into contact with the first surface of thefirst substrate 11, the flow of current from the first electrode 13_5 tothe second electrode 23_5 can be completely blocked. This is so, becausethere is no electrode at the contact areas. On the other hand, when aforce is received in the first linear direction X1, which is thehorizontal direction, the first force sensing layer 14_5 may come intodirect contact with the second electrode 23_5, so that a current mayflow. Accordingly, it is possible to determine whether there is a shearforce and to sense its magnitude.

FIG. 8 is cross-sectional view of a force sensor according to yetanother exemplary embodiment of the present invention.

A force sensor 1_6 according to the exemplary embodiment shown in FIG. 8is substantially identical to the force sensor 1 shown in FIG. 1 exceptthat first and second insulating patterns 16 and 26 are disposed on thefirst force sensing layer 14 disposed on the first protrusion 12 and onthe second electrode 23 disposed on the second protrusion 22,respectively.

For example, the first insulating pattern 16 is disposed on the firstforce sensing layer 14 of a first sensor element 10_6, and the secondinsulating pattern 26 is disposed on the second electrode 23 of a secondsensor element 206. The first insulating pattern 16 overlaps with thecenter 12 c of the first protrusion 12 but not with the peripheralportion of the first protrusion 12; therefore, the first force sensinglayer 14 on the peripheral portion of the first protrusion 12 isexposed. The second insulating pattern 26 overlaps with the center 22 cof the second protrusion 22 but not with the peripheral portion of thesecond protrusion 22; therefore, the second electrode 23 on theperipheral portion of the second protrusion 22 is exposed. The firstinsulating pattern 16 and the second insulating pattern 26 may havesubstantially the same shape as the first protrusion opened portion EX1and the second protrusion opened portion EX2 of FIG. 7 when viewed fromabove.

According to the present embodiment, when the force sensor 1_6 receivesa force in the thickness directions Z1 and Z2, the first insulatingpattern 16 on the center 12 c of the first protrusion 12 comes intocontact with the first surface of the second substrate 21, and thesecond insulating pattern 26 on the center 22 c of the second protrusion22 comes into contact with the first surface of the first substrate 1_1,as a result, the flow of the current from the first electrode 13 to thesecond electrode 23 can be completely blocked. This is so, because thereis no electrode at the contact areas, and thus, insulation is achievedby the insulating patterns 16 and 26. On the other hand, when a force isreceived in the first linear direction X1, which is the horizontaldirection, the first force sensing layer 14 may come into direct contactwith the second electrode 23, so that a current may flow. Accordingly,it is possible to determine whether there is a shear force and to senseits magnitude.

FIG. 9 is a cross-sectional view of a force sensor according to yetanother exemplary embodiment of the present invention.

A force sensor 1_7 according to the exemplary embodiment shown in FIG. 9is substantially identical to the force sensor 1 shown in FIG. 1 exceptthat a first protrusion 12_7 p is integrally formed on a first bodyportion 12_7 s covering the first surface of the first substrate 11, anda second protrusion portion 22_7 p is integrally formed on a second bodyportion 22_7 s covering the side surface of the second substrate 21.

For example, a first sensor element 10_7 includes a first protrusionlayer 12_7 including the first body portion 12_7 s and the firstprotrusion portion 12_7 p protruded from the surface of the first bodyportion 12_7 s in the first thickness direction Z1. A second sensorelement 20_7 includes a second protrusion layer 22_7 including thesecond body portion 22_7 s and the second protrusion portion 22_7 pprotruded from the surface of the second body portion 22_7 s in thesecond thickness direction Z2. The first body portion 12_7 s may coverthe entire first surface of the first substrate 11, and the second bodyportion 22_7 s may cover the entire first surface of the secondsubstrate 21. The first protrusion portion 12_7 p and the secondprotrusion portion 22_7 p correspond to the first protrusion 12 and thesecond protrusion 22 of FIG. 1, respectively.

The force sensor according to the present embodiment can be used todetermine whether there is a shear force and to sense its magnitude, inthe same manner described above with reference to FIG. 1.

FIG. 10 is cross-sectional view of a force sensor according to yetanother exemplary embodiment of the present invention.

According to the exemplary embodiment of FIG. 10, a first protrusion12_8 of a first sensor element 10_8 and a second protrusion 22_8 of asecond sensor element 20_8 may have a trapezoidal cross section.

For example, the first protrusion 12_8 and the second protrusion 22_8may have a pyramid-like, rectangular column shape that becomes narrowerin the protruding direction. It is to be understood, however, that thepresent invention is not limited thereto. The first protrusion 12_8 andthe second protrusion 22_8 may have other polygonal column orcylindrical shapes. The side inclination angles of the first protrusion12_8 and the second protrusion 22_8 may be, but are not limited to,equal to each other.

According to the present embodiment, when the force sensor 1_8 receivesa shearing force, the contact area between the first force sensing layer14 on the second side of the first protrusion 12_8 and the secondelectrode 23 on the first side of the second protrusion 22_8 becomeslarger than that of the force sensor 1 of FIG. 1. Accordingly, theamount of current flowing from the first electrode 13 to the secondelectrode 23 increases, allowing for more precise sensing.

Hereinafter, the above-described force sensor, according to an exemplaryembodiment of the present invention, will be described in detail.

FIG. 11 is a plan view showing the layout of a force sensor according toan exemplary embodiment of the present invention when viewed from above.

Referring to FIG. 11, the force sensor includes a plurality of firstelectrodes 130 extending in a first extending direction and a pluralityof second electrodes 230 extending in a second extending direction. InFIG. 11, the first extending direction refers to a lateral direction(e.g., from left to right), and the second extending direction refers toa longitudinal direction (e.g., from top to bottom (or upward/downward)in a plan view), such that they intersect each other.

The force sensor includes a plurality of sensing cells SR. The sensingcells SR are arranged in a matrix. In the array of sensing cells SRarranged in the matrix, the pitch of each of the row extending direction(e.g., a horizontal direction) and the column extending direction (e.g.,a vertical direction) may range from 2 mm to 8 mm. In an exemplaryembodiment of the present invention, the pitch of each of the horizontaldirection and the vertical direction of the array of sensing cells SRmay be approximately 4 mm.

Each of the sensing cells SR includes a plurality of sub-sensing regionsSR1, SR2, SR3 and SR4. For example, each of the sensing cells SR mayinclude a first sub-sensing region SR1, a second sub-sensing region SR2,a third sub-sensing region SR3, and a fourth sub-sensing region SR4. Thesub-sensing regions SR1, SR2, SR3 and SR4 may be located at theintersections of the first electrodes 130 and the second electrodes 230,respectively. In each of the sensing cells SR, the sub-sensing regionsSR1, SR2, SR3 and SR4 may be disposed adjacent to one another. Forexample, the sub-sensing regions SR1, SR2, SR3 and SR4 in a singlesensing cell SR may be arranged in a two-by-two matrix.

For example, assume that the first sub-sensing region SR1 is formed atthe intersection between the m^(th) first electrode 130 and the n^(th)second electrode 230. Then, the second sub sensing region SR2 may beformed at the intersection between the m^(th) first electrode 130, whichis adjacent to right side of the first sub sensing region SR1, and the(n+1)^(th) second electrode 230. The third sub sensing region SR3 may beformed at the intersection between the (m+1)^(th) first electrode 130,which is adjacent to the lower side of the first sub-sensing region SR1,and the n^(th) second electrode 230. The fourth sub sensing region SR4may be formed at the intersection between the (m+1)^(th) first electrode130, which is adjacent to the lower side of the second sub sensingregion SR2 and adjacent to the right side of the third sub sensingregion SR3, and the (n+1)^(th) second electrode 230.

The sub-sensing regions SR1, SR2, SR3 and SR4 can sense shear forces indifferent directions. For example, the first sub-sensing region SR1 maysense a rightward shear force, the second sub-sensing region SR2 maysense a leftward shearing force, the third sub-sensing region SR3 maysense a downward shearing force, and the fourth sub-sensing regions SR4may sense an upward shearing force. It is to be understood, however,that the present invention is not limited thereto. The direction of theshearing force sensed by each of the sub-sensing regions SR1, SR2, SR3and SR4 may be variously modified.

The pitch of each of the row extending direction (e.g., the horizontaldirection) and the column extending direction (e.g., the verticaldirection) of each of the sub-sensing regions SR1, SR2, SR3 and SR4 mayrange from 1 mm to 4 mm. In an exemplary embodiment of the presentinvention in which the pitch in the horizontal and vertical directionsof the array of sensing cells SR is approximately 4 mm, the pitch ofeach of the sub-sensing regions SR1, SR2, SR3 and SR4 may beapproximately 2 mm or less (e.g., approximately 80% to 90%).

FIG. 12 is an enlarged view of one of the sensing cells of FIG. 11,according to an exemplary embodiment of the present invention. FIG. 13is a plan view showing the layout of a first sensor element of FIG. 12,according to an exemplary embodiment of the present invention. FIG. 14is a plan view showing the layout of a second sensor element of FIG. 12,according to an exemplary embodiment of the present invention. FIG. 15is a cross-sectional view taken along line XV-XV′ shown in FIG. 12,according to an exemplary embodiment of the present invention.

Referring to FIGS. 12 to 15, a first sensor element includes a firstsubstrate 110, a first protrusion 120, a first electrode 130 and a firstforce sensing layer 140 stacked on the first substrate 110. A secondsensor element includes a second substrate 210, a second protrusion 220and a second electrode 230 stacked on the second substrate 210.

The first protrusion 120 and the second protrusion 220 form a pair ofprotrusions. In FIG. 12, the first protrusion 120 is disposed adjacentto the right side of the second protrusion 220 in the first sub-sensingregion SR1, the first protrusion 120 is disposed adjacent to the leftside of the second protrusion 220 in the second sub-sensing region SR2,the first protrusion 120 is disposed adjacent to the lower side of thesecond protrusion 220 in the third sub-sensing region SR3, and the firstprotrusion 120 is disposed adjacent to the upper side of the secondprotrusion 220 in the fourth sub-sensing region SR4.

Each of the first to fourth sub-sensing regions SR1, SR2, SR3 and SR4may include a plurality of pairs of protrusions. Although the pairs ofprotrusions are arranged in a four-by-four matrix in each of the firstto fourth sub-sensing regions SR1, SR2, SR3 and SR4, the numbers of thepairs of protrusions and their arrangement are not limited thereto.

The first sensor element may include a plurality of first opening areasOP1 in which each of the first electrode 130 and the first force sensinglayer 140 are not disposed to thus expose the first surface of the firstsubstrate 110. The second sensor element may include a plurality ofsecond opening areas OP2 in which the second electrode 230 is notdisposed to thus expose the first surface of the second substrate 210.Each of the first opening areas OP1 may be associated with the secondprotrusion 220 of the second sensor element facing it, and each of thesecond opening areas OP2 may be associated with the first protrusion 120of the first sensor element facing it. When the number of the first andsecond protrusions 120 and 220 is sixteen, the number of the firstopening areas OP1 and the number of the second opening areas OP2 may besixteen. The shape of the first opening area OP1 and the second openingarea OP2 may be, but is not limited to, a circle, an ellipse, arectangle, a rectangle having rounded corners, and the like, when viewedfrom above.

In the first sub-sensing region SR1, the first opening area OP1 isformed adjacent to the left side of the first protrusion 120 to overlapwith the respective second protrusion 220 (e.g., the second protrusion220 of the pair). The first opening area OP1 formed adjacent to the leftside of a particular first protrusion 120 may not overlap with anotherfirst protrusion 120 adjacent to the left side of the particular firstprotrusion 120. In other words, the right side surface of the firstprotrusion 120 may be spaced apart from that first opening area OP1.

In the second sub-sensing region SR2, the first opening area OP1 isformed adjacent to the right side of the first protrusion 120 to overlapwith the respective second protrusion 220 (e.g., the second protrusion220 of the pair). The first opening area OP1 formed adjacent to theright side of a particular first protrusion 120 may not overlap withanother first protrusion 120 adjacent to the right side of theparticular first protrusion 120. In other words, the left side surfaceof the first protrusion 120 may be spaced apart from that first openingarea OP1.

In the third sub-sensing region SR3, the first opening area OP1 isformed adjacent to the upper side of the first protrusion 120 whenviewed from the top to overlap with the respective second protrusion 220(e.g., the second protrusion 220 of the pair). The first opening areaOP1 formed adjacent to the upper side of a particular first protrusion120 may not overlap with another first protrusion 120 adjacent to theupper side of the particular first protrusion 120. In other words, thelower side surface of the first protrusion 120 may be spaced apart fromthe first opening area OP1 formed adjacent to the upper side of thefirst protrusion 120.

In the fourth sub-sensing region SR4, the first opening area OP1 isformed adjacent to the lower side of the first protrusion 120 whenviewed from the top to overlap with the respective second protrusion 220(e.g., the second protrusion 220 of the pair). The first opening areaOP1 formed adjacent to the lower side of a particular first protrusion120 may not overlap with another first protrusion 120 adjacent to thelower side of the particular first protrusion 120. In other words, theupper side surface of the first protrusion 120 may be spaced apart fromthe first opening area OP1 formed adjacent to the lower side of thefirst protrusion 120.

In each of the first to fourth sub-sensing regions SR1, SR2, SR3 andSR4, the width (e.g., the width in the lateral direction) of the firstopening area OP1 is equal to or greater than the width of the secondprotrusion 220 facing it. For example, the width of the first openingarea OP1 (for example, the width in the lateral direction in the firstand second sub-sensing regions SR1 and SR2, and the width in thevertical direction in the third and fourth sub-sensing regions SR3 andSR4) may be one to four times the width of the second protrusion 220facing it. For example, and the width of the first opening area OP1 maybe approximately two times the width of the second protrusion facing it.

FIG. 16 is a flowchart for illustrating a method for sensing a shearforce and utilizing information by a force sensor according to anexemplary embodiment of the present invention.

Referring to FIG. 16, when a touch event generating a shear force occurs(step S1), it is determined whether there is a change in signal in thefirst to fourth sub-sensing regions SR1, SR2, SR3 and SR4 (step S2). Bydoing so, it is possible to determine in which direction the shear forceis generated in a plane (step S3), and the intensity of the shear forcecan be determined (step S4) based on the amount of the change in thesignal. Once the direction and intensity of the shear force aredetermined, a corresponding operation may be carried out on a UserInterface (UI) (step S4).

A process of determining the direction and intensity of a touch eventgenerating a shear force will be described in detail with referenceFIGS. 17 to 20.

FIG. 17 is a plan view showing a method of detecting a sensing signalwhen a rightward shearing force is received, according to an exemplaryembodiment of the present invention. FIG. 18 is a plan view showing amethod of detecting a sensing signal when a leftward shearing force isreceived, according to an exemplary embodiment of the present invention.FIG. 19 is a plan view showing a method of detecting a sensing signalwhen a downward shearing force is received, according to an exemplaryembodiment of the present invention. FIG. 20 is a plan view showing amethod of detecting a sensing signal when an upward shearing force isreceived, according to an exemplary embodiment of the present invention.

Initially, when a shear force is applied toward the right side as shownin the plan view of FIG. 17, the second substrate 210 is pushed to theright side, such that the relative positional relationship of the firstprotrusion 120 and the second protrusion 220 in each pair is changed.

In the first sub-sensing region SR1, the second protrusion 220 of eachpair is moved toward the first protrusion 120, such that the secondelectrode 230 thereon comes into contact with the first force sensinglayer 140. As a result, a force in the horizontal direction may beapplied. On the other hand, in the second sub-sensing region SR2, thesecond protrusions 220 move away from the first protrusions 120. In thethird and fourth sub-sensing regions SR3 and SR4, the position of thesecond protrusions 220 relative to the first protrusion 120 is changedwhile substantially keeping the distance therebetween in the verticaldirection. As a result, the first protrusions 120 and the secondprotrusions 220 are not pressed.

Therefore, when a driving voltage of a certain level is applied to thefirst electrode 130 (e.g., the electrode in the upper row in FIG. 17) ofthe first sub-sensing region SR1, current flows to the second electrode230 (e.g., the electrode in the left column in FIG. 17) of the firstsub-sensing region SR1. A driving voltage of a certain level is alsoapplied to the second sub-sensing region SR2 sharing the first electrode130 with the first sub-sensing region SR1. However, the first electrode130 is not electrically connected to the second electrode 230 in thesecond sub-sensing region SR2. Accordingly, no current flows to thesecond electrode 230 (e.g., the electrode in the right column in FIG.17) of the second sub-sensing region SR2.

On the other hand, the electrode in the left column, which is the secondelectrode 230, is disposed across the first sub-sensing region SR1 andthe third sub-sensing region SR3. In other words, the first sub-sensingregion SR1 and the third sub-sensing region SR3 share the same secondelectrode 230. Therefore, it is useful to determine which sub-sensingregion the current flowing in the electrode in the left columnoriginates from. By applying the driving voltage of 0 V to another firstelectrode 130 (e.g., the electrode in the lower row in FIG. 17) whichdoes not belong to the first sub-sensing region SR1 while applying adriving voltage of high-level to the electrode in the upper row which isthe first electrode 130, it is possible to determine that the currentflowing in the electrode in the left column originates from the firstsub-sensing region SR1. As a result, it is possible to determine that ashearing force is generated toward the right side in the sensing cellSR. Further, it is possible to determine the magnitude of the shearforce based on the amount of current flowing in the second electrode 230(e.g., the electrode in the left column in the drawings) of the firstsub-sensing region SR1.

When a shear force is applied toward the left side as shown in the planview of FIG. 18, the second substrate 210 is pushed to the left side,such that the relative positional relationship of the first protrusion120 and the second protrusion 220 in each pair is changed.

In the second sub-sensing region SR2, the second protrusion 220 of eachpair is moved toward the first protrusion 120, such that the secondelectrode 230 thereon comes into contact with the first force sensinglayer 140. As a result, a force in the horizontal direction may beapplied. On the other hand, in the first sub-sensing region SR1, thesecond protrusions 220 move away from the first protrusions 120. In thethird and fourth sub-sensing regions SR3 and SR4, the position of thesecond protrusions 220 relative to the first protrusion 120 is changedwhile substantially keeping the distance therebetween in the verticaldirection. As a result, the first protrusions 120 and the secondprotrusions 220 are not pressed.

By applying the driving voltage of 0 V to another first electrode 130(e.g., the electrode in the second row (e.g., lower row) in FIG. 18)which does not belong to the second sub-sensing region SR2 whileapplying a driving voltage of a certain level to the first electrode 130of the second sub-sensing region SR2 (e.g., the electrode in the firstrow (e.g., upper row) in FIG. 18), a current may flow to the secondelectrode 230 (the electrode in the second column (e.g., right column)in FIG. 18) of the second sub-sensing region SR2. In this case, it ispossible to determine that the shear force is generated toward the leftside in the sensing cell SR based on the current. In addition, themagnitude of the shear force can be determined based on the amount ofcurrent.

When a shear force is applied toward the lower side as shown in the planview of FIG. 19, the second substrate 210 is pushed to the lower side,such that the relative positional relationship of the first protrusion120 and the second protrusion 220 in each pair is changed.

In the third sub-sensing region SR3, the second protrusion 220 of eachpair is moved toward the first protrusion 120, such that the secondelectrode 230 thereon comes into contact with the first force sensinglayer 140. As a result, a force in the horizontal direction may beapplied. On the other hand, in the fourth sub-sensing region SR4, thesecond protrusions 220 move away from the first protrusions 120. In thefirst and second sub-sensing regions SR1 and SR2, the position of thesecond protrusions 220 relative to the first protrusions 120 is changedwhile substantially keeping the distance therebetween in the horizontaldirection. As a result, the first protrusions 120 and the secondprotrusions 220 are not pressed.

By applying the driving voltage of 0 V to another first electrode 130(e.g., the electrode in the first row (e.g., upper row) in FIG. 19)which does not belong to the second sub-sensing region SR2 whileapplying a driving voltage of a certain level to the first electrode 130of the third sub-sensing region SR3 (e.g., the electrode in the secondrow (e.g., lower row) in FIG. 19), a current may flow to the secondelectrode 230 (e.g., the electrode in the first column (e.g., leftcolumn) in FIG. 19) of the third sub-sensing region SR3. Therefore, itis possible to determine that the shear force is generated toward thelower side in the sensing cell SR based on the current. In addition, themagnitude of the shear force can be determined based on the amount ofcurrent.

When a shear force is applied toward the upper side as shown in the planview of FIG. 20, the second substrate 210 is pushed to the lower side,such that the relative positional relationship of the first protrusion120 and the second protrusion 220 in each pair is changed.

In the fourth sub-sensing region SR4, the second protrusion 220 of eachpair is moved toward the first protrusion 120, such that the secondelectrode 230 thereon comes into contact with the first force sensinglayer 140. As a result, a force in the horizontal direction may beapplied. On the other hand, in the third sub-sensing region SR3, thesecond protrusions 220 move away from the first protrusions 120. In thefirst and second sub-sensing regions SR1 and SR2, the position of thesecond protrusions 220 relative to the first protrusions 120 is changedwhile substantially keeping the distance therebetween in the horizontaldirection. As a result, the first protrusions 120 and the secondprotrusions 220 are not pressed.

By applying the driving voltage of 0 V to another first electrode 130(e.g., the electrode in the first row (e.g., upper row) in FIG. 20)which does not belong to the fourth sub-sensing region SR4 whileapplying a driving voltage of a certain level to the first electrode 130of the fourth sub-sensing region SR4 (e.g., the electrode in the secondrow (e.g., lower row) in FIG. 20), a current may flow to the secondelectrode 230 (e.g., the electrode in the second column (e.g., lowercolumn) in FIG. 20) of the fourth sub-sensing region SR4. Therefore, itis possible to determine that the shear force is generated toward theupper side in the sensing cell SR based on the current. In addition, themagnitude of the shear force can be determined based on the amount ofcurrent.

The shear force input to the force sensor may have a direction otherthan the upward, downward, leftward, and rightward. In this case, thesensing currents may be detected in two or more sub-sensing regions. Forexample, when a right-upward shear force is applied to the force sensor,the shear force may be divided into the rightward shear force componentand the upward shear force component. Therefore, a sensing current maybe detected from each of the first sub-sensing region SR1 by sensing therightward shear force and the fourth sensing region SR4 by sensing theupward shearing force. By expressing the shear force detected from eachof the sub-sensing regions as vectors and adding up these vectors, thedirection and magnitude of the actual shear force can be calculated. Inthis way, the shear force in 360° and its magnitude can be measured fromthe sub-sensing regions SR1, SR2, SR3 and SR4 by sensing the shear forcein four directions.

FIG. 21 is a plan view showing the layout of a first sensor element of aforce sensor according to another exemplary embodiment of the presentinvention. The exemplary embodiment of FIG. 21 illustrates that thefirst opening areas OP1 associated with two or more protrusion pairs canbe connected to each other.

Referring to FIG. 21, in the first and second sub-sensing regions SR1and SR2 of the first sensor element, a single first opening area OP1′ isformed adjacent to a plurality of first protrusions 120 adjacent to eachother in the vertical direction (e.g., first protrusions 120 belongingto the same column). In the third and fourth sub-sensing regions SR3 andSR4, a single first opening area OP1′ is formed adjacent to a pluralityof first protrusions 120 adjacent to each other in the horizontaldirection (e.g., first protrusions 120 belonging to the same row). Thefirst opening area OP1′ may have a shape extending in the verticaldirection or the horizontal direction. Although not shown in FIG. 21,for the second sensor element, the second opening areas OP2 associatedwith two or more protrusion pairs may be connected to each other in thesame manner as the first opening areas OP1′.

According to this exemplary embodiment, although the single firstopening OP1′ is extended in one direction to be formed adjacent to theplurality of protrusions 120, the first electrodes 130 are notdisconnected by the first opening areas OP1′ but instead are connectedto one another. Therefore, it is possible to detect a shear force insubstantially the same manner as described in reference to FIG. 11.

FIG. 22 is a plan view showing the layout of a force sensor according toyet another exemplary embodiment of the present invention. FIG. 23 is across-sectional view taken along line XXIII-XXIII′ of FIG. 22, accordingto an exemplary embodiment of the present invention. The embodimentshown in FIGS. 22 and 23 differs from the embodiment shown in FIG. 11 inthat FIGS. 22 and 23 further include a pressure sensing region forsensing a pressure in the thickness direction.

Referring to FIG. 22, an additional first electrode 130 may be disposedbetween the first electrode 130 of the first and second sub-sensingregions SR1 and SR2, and the first electrode 130 of the third and fourthsub-sensing regions SR3 and SR4 of the force sensor. In addition, anadditional second electrode 230 may be disposed between the secondelectrode 230 of the first and third sub-sensing regions SR1 and SR3,and the second electrode 230 of the second and fourth sub-sensingregions SR2 and SR4 of the force sensor. A pressure sensing region SR0may be located at the intersection of the additional first electrode 130and the additional second electrode 230. In other words, the sensingcell SR may further include the pressure sensing region SR0, in additionto the first to fourth sub-sensing regions SR1, SR2, SR3, and SR4. Thewidth of the first and second electrodes 130 and 230 forming thepressure sensing region SR0 may be smaller than the width of the firstelectrode 130 and the second electrode 230 forming the sub-sensingregions SR1, SR2, SR3 and SR4. However, the present invention is notlimited thereto.

Referring to FIGS. 22 and 23, in the pressure sensing region SR0, thefirst sensor element may include a plurality of first protrusions 120,and the second sensor element may include a plurality of secondprotrusions 220. The first protrusions 120 may face the secondprotrusions 220 such that the centers of the first protrusions 120 arealigned with the centers of the second protrusions 220 in the pressuresensing region SR0, unlike the other sub-sensing regions SR1, SR2, SR3and SR4. It is to be understood, however, that the present invention isnot limited thereto. For example, the first protrusion 120 and thesecond protrusion 220 may overlap with each other in the thicknessdirection.

In the pressure sensing region SR0, a first sensor element and a secondsensor element may not include an opening area. In other words,similarly to the exemplary embodiment shown in FIG. 6, the firstelectrode 130 and the first force sensing layer 140 are disposed tocover the entire area of the first surface of the first substrate 110,and the second electrode 230 may cover the entire area on the firstsurface of the second substrate 210.

When the force sensor receives a force in the second thickness directionZ2, the second protrusion 220 approaches the first protrusion 120, suchthat the first electrode 130, the first force sensing layer 140, thesecond electrode 230 can come into contact one another. Accordingly, thesensing current can be sensed in the pressure sensing region SR0, suchthat it is possible to determine whether there is a force in thethickness direction and to sense the magnitude thereof, if such forceexists.

FIG. 24 is a plan view showing the layout of a force sensor according toyet another exemplary embodiment of the present invention. The exemplaryembodiment shown in FIG. 24 illustrates that a force sensor may includesub-sensing regions for detecting a shearing force in directions otherthan the upward, downward, leftward, and rightward directions.

A force sensor according to the exemplary embodiment shown in FIG. 24 issubstantially identical to the exemplary embodiment shown in FIG. 22except that a sensing cell SR includes a pressure sensing region SR0 andeight sub-sensing regions SR1, SR2, SR3, SR4, SR5, SR6, SR7 and SR8. Thepressure sensing region SR0 and the eight sub-sensing regions SR1 to SR8may be arranged in a three-by-three matrix.

In a single sensing cell SR, three first electrodes 130 and three secondelectrodes 230 may be disposed. The sub-sensing regions SR1 to SR8 andthe pressure sensing regions SR0 are arranged at the intersections ofthe first electrodes 130 and the second electrodes 230.

According to an exemplary embodiment of the present invention, the firstsub-sensing region SR1 is configured to sense a rightward shear forceand may be formed at the intersection of the first electrode 130 in thefirst row (e.g., upper row) and the second electrode 230 in the secondcolumn (e.g., middle column). The second sub-sensing region SR2 isconfigured to sense a leftward shear force and may be formed at theintersection of the first electrode 130 in the third row (e.g., lowerrow) and the second electrode 230 in the second column (e.g., middlecolumn). The third sub-sensing region SR3 is configured to sense adownward shear force and may be formed at the intersection of the firstelectrode 130 in the second row (e.g., middle row) and the secondelectrode 230 in the first column (e.g., left column). The fourthsub-sensing region SR4 is configured to sense an upward shear force andmay be formed at the intersection of the first electrode 130 in thesecond row (e.g., middle row) and the second electrode 230 in the thirdcolumn (e.g., right column). The fifth sub-sensing region SR5 isconfigured to sense a right-downward shear force (at an angle of 45°between the rightward and the downward forces, for example) and may beformed at the intersection of the first electrode 130 in the first rowand the second electrode 230 in the third column. The sixth sub-sensingregion SR6 is configured to sense a left-downward shear force and may beformed at the intersection of the first electrode 130 in the third rowand the second electrode 230 in the third column. The seventhsub-sensing region SR7 is configured to sense a left-upward shear forceand may be formed at the intersection of the first electrode 130 in thethird row and the second electrode 230 in the first column. The eighthsub-sensing region SR8 is configured to sense a right-upward shear forceand may be formed at the intersection of the first electrode 130 in thefirst row and the second electrode 230 in the first column. The pressuresensing region SR0 is configured to sense a force in the thicknessdirection and may be formed at the intersection of the first electrode130 in the second row and the second electrode 230 in the second column.

In the sub-sensing regions SR1 to SR8, the first protrusions 120 arepositioned closer to the direction of the shearing force to be detectedthan the respective second protrusions 220. For example, in the fifthsub-sensing region SR5 for sensing the right-downward shear force, thefirst protrusions 120 are disposed adjacent to the lower right side ofthe respective second protrusions 220.

In the pressure sensing region SR0, the first protrusion 120 and thesecond protrusion 220 of each pair may overlap each other, and thenumber of the pairs, e.g., four, may be less than the number of thepairs in the sub-sensing regions, e.g., 16. It is to be understood,however, that the present invention is not limited thereto.

According to the present embodiment, the force sensor further includesthe sub-sensing regions for detecting right-upward, right-downward,left-upward and left-downward shearing forces as well as than theupward, downward, leftward, and rightward shear forces, so that it ispossible to more precisely detect the directions of the shear forces.

Hereinafter, a variety of shapes and layouts of a supporter of a forcesensor will be described. FIGS. 25 to 27 are plan views showing thelayouts of a force sensor according to a variety of exemplaryembodiments of the present invention.

Referring to FIG. 25, a first sensor element 10 and a second sensorelement 20 overlap with each other in the thickness direction and arecoupled with each other by a supporter 31. The supporter 31 of the forcesensor may be disposed along the edge of the first sensor element 10 andthe second sensor element 20. The force sensor may include an array ofsensing cells SR arranged in a matrix, and the supporter 31 may surroundthe array of sensing cells SR. The supporter 31 may not overlap with thesensing cells SR. The supporter 31 may be disposed in the form of acontinuous line and may have a closed curve shape when viewed from thetop, e.g., above.

The embodiment shown in FIG. 26 differs from the embodiment shown inFIG. 25 in that a supporter 32 of a force sensor is disposed in the formof an intermittent line. As shown in FIG. 26, the supporter 32 isdisposed along the edge of a first sensor element 10 and a second sensorelement 20, and may have a stitch shape (or a broken shape) of separatedislands.

According to the exemplary embodiment shown in FIG. 27, the supporters33 of the force sensor may be disposed inside the array of the sensingcells SR. As shown in FIG. 27, a plurality of the supporters 33 may bedisposed along the boundaries of the plurality of sensing cells SR. Thesupporters 33 are separated from one another and spaced apart from oneanother by a regular spacing. For example, each of the supporters 33 maybe disposed for every sensing cell SR or for several sensing cells SR.The supporters 33 may have a cross shape. The horizontal length of thesupporters 33 may be equal to the vertical length of the supporters 33,and the lengths of the supporters 33 may be smaller than the width ofthe sensing cells SR. It is to be understood, however, that the presentinvention is not limited thereto. For example, the supporters 33 mayhave various island-like shapes other than the cross shape.

Although not shown in FIG. 27, the supporters 33 may also be disposedbetween sub-sensing regions (see SR1, SR2, SR3 and SR4 in FIG. 11). Theexemplary embodiment shown in FIG. 27 may be combined with theembodiment of FIG. 25 or 26. In other words, supporters (31, 32 or 33)may be disposed on the edge of the first sensor element 10 and thesecond sensor element 20 and as well as inside the array of sensingcells SR.

The force sensor as described above may be applied to various electronicdevices including display devices.

FIGS. 28 and 29 are views of electronic devices including force sensorsaccording to exemplary embodiments of the present invention.

FIG. 28(a) illustrates an example where a force sensor 301 overlaps withthe display screen of a smartphone 401. The force sensor 301 recognizesa shearing force, so that a variety of applications can be achieved,e.g., the display device may display an image that a paper is turnedover.

FIG. 28(b) illustrates an example where a force sensor 302 is disposedat either side of the longer edge of a smartphone 402. The force sensor302 disposed at the both longer sides may be used for receiving a touchinput or in place of physical buttons.

FIG. 28(c) illustrates an example where a force sensor 303 is disposedat side displays of a multifaceted display device 403.

FIG. 29(a) illustrates an example where a force sensor 304 is disposedon the side portion of a smart watch 404 to be utilized as an inputdevice.

FIG. 29(b) illustrates an example where a force sensor 305 is disposedat the center of glasses in a head-mounted display device 405 to serveas a control key of the head-mounted display device 405.

FIG. 29(c) illustrates an example where a force sensor 306 is disposedat least on a part of the display screen of a game console or asmartphone 406 to be used in place of control buttons of a joystick.

FIG. 29(d) illustrates an example where a force sensor 307 is includedin a display device of a navigation device or a center panel inside avehicle 407. For example, the force sensor 307 may be used as an inputmeans for various devices such as an air conditioner and an audiodevice, which are located in the center panel of the vehicle 407.

The applications of the force sensor are not limited to those shown inthe drawings, and the force sensor may be applicable to various types ofinput means for other electronic devices.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

What is claimed is:
 1. A force sensor, comprising: a first surface and asecond surface facing each other in a first direction; a firstprotrusion protruded from the first surface toward the second surface; afirst electrode on the first protrusion; a first force sensing layer onthe first electrode; a second protrusion protruded from the secondsurface toward the first surface; and a second electrode on the secondprotrusion, wherein the first protrusion and the second protrusion arenot overlapped with each other or are partially overlapped with eachother, wherein a center of the first protrusion is spaced apart from acenter of the second protrusion in a second direction perpendicular tothe first direction, and wherein the center of the first protrusionoverlaps a portion of the second surface not covered by the secondelectrode.
 2. The force sensor of claim 1, wherein a space between thecenter of the first protrusion and the center of the second protrusionin the second direction is smaller than a sum of a width of the firstprotrusion and a width of the second protrusion.
 3. The force sensor ofclaim 2, wherein each of the first protrusion and the second protrusioncomprises a first side and a second side opposite to the first sidealong the second direction, and wherein the second side of the firstprotrusion does not overlap with the second protrusion in the firstdirection.
 4. The force sensor of claim 3, wherein the second side ofthe first protrusion is spaced apart from the first side of the secondprotrusion in the second direction.
 5. The force sensor of claim 2,wherein each of the first protrusion and the second protrusion comprisesa first side and a second side opposite to the first side along thesecond direction, and wherein the second side of the first protrusionoverlaps with the second protrusion in the first direction.
 6. The forcesensor of claim 1, further comprising: a first opening on the firstsurface, wherein the first electrode and the first force sensing layerare not disposed in the first opening; and a second opening on thesecond surface, wherein the second electrode is not disposed in thesecond opening, wherein the center of the second protrusion overlapswith the first opening, and the center of the first protrusion overlapswith the second opening.
 7. The force sensor of claim 6, wherein thefirst protrusion is spaced apart from the second surface and the secondprotrusion is spaced apart from the first surface when the force sensoris not pressed.
 8. The force sensor of claim 7, wherein the firstprotrusion comes in contact with the second surface and the secondprotrusion comes in contact with the first surface when the force sensoris pressed in the first direction.
 9. The force sensor of claim 1,wherein the first force sensing layer on the first protrusion comes incontact with the second electrode on the second protrusion in responseto an externally applied force.
 10. The force, sensor of claim 1,wherein the first force sensing layer includes a pressure sensitivematerial with a resistance that varies depending on a pressure appliedthereto.
 11. The force sensor of claim 1, further comprising: a secondforce sensing layer on the second electrode.
 12. The force sensor ofclaim 1, wherein each of the first protrusion and the second protrusionhas a dome shape.
 13. The force sensor of claim 1, further comprising:an insulating layer on the first force sensing layer, wherein the firstelectrode and the first force sensing layer extend to an area facing thesecond protrusion, and wherein the insulating layer covers the firstforce sensing layer in the area facing the second protrusion.
 14. Theforce sensor of claim 1, further comprising: an insulating layer on thesecond electrode, wherein the second electrode extends to an area facingthe first protrusion, and wherein the insulating layer covers a part ofthe second electrode on the area facing the first protrusion.
 15. Theforce sensor of claim 1, further comprising: an insulating patterndisposed on the first force sensing layer, wherein the insulatingpattern overlaps with the center of the first protrusion and does notoverlap with a side portion of the first protrusion.
 16. The forcesensor of claim 1, further comprising: an insulating pattern disposed onthe second electrode, wherein the insulating pattern overlaps with thecenter of the second protrusion and does not overlap with a side portionof the second protrusion.
 17. A force sensor, comprising: a first sensorelement comprising a first substrate, a first protrusion disposed on thefirst substrate, a first electrode on the first protrusion, and a firstforce sensing layer on the first electrode; a second sensor elementcomprising a second substrate, a second protrusion disposed on thesecond substrate, and a second electrode disposed on the secondprotrusion; a first opening on the first substrate, wherein at least oneof the first electrode and the first force sensing layer is not disposedin the first opening, and a second opening on the second substrate,wherein the second electrode is not disposed in the second opening,wherein a center of the first protrusion is spaced apart from a centerof the second protrusion in a first direction, wherein the center of thesecond protrusion overlaps with the first opening, and the center of thefirst protrusion overlaps with the second opening, wherein the firstforce sensing layer faces the second substrate, and wherein the firstprotrusion and the second protrusion do not overlap with each other, orat least partially overlap with each other.
 18. The force sensor ofclaim 17, wherein a spacing between the center of the first protrusionand the center of the second protrusion in the first direction issmaller than a sum of a width of the first protrusion and a width of thesecond protrusion.
 19. The force sensor of claim 18, wherein each of thefirst protrusion and the second protrusion comprises a first side and asecond side along the first direction, and wherein the second side ofthe first protrusion does not overlap with the second protrusion in tosecond direction perpendicular to the first direction.
 20. The forcesensor of claim 19, wherein the second side of the first protrusion isspaced apart from the first side of the second protrusion in the firstdirection.
 21. The force sensor of claim 18, wherein each of the firstprotrusion and the second protrusion comprises a first side and a secondside along the first direction, and wherein the second side of the firstprotrusion overlaps with the second protrusion in a second directionperpendicular to the first direction.
 22. A force sensor, comprising: aplurality of sensing cells; a plurality of first electrodes extended ina first extending direction; and a plurality of second electrodesextended in a second extending direction and intersecting with the firstelectrodes; wherein at least one of the sensing cells includes aplurality of sub-sensing regions located at intersections between thefirst electrodes and the second electrodes, wherein at least one of thesub-sensing regions comprises: a first surface and a second surfacefacing each other in a thickness direction the force sensor, a pluralityof protrusions protruded from the first surface toward the secondsurface, one of the first electrodes on the plurality of firstprotrusions, and a first force sensing layer on the one first electrode,a plurality of second protrusions protruded from the second surfacetoward the first surface, and one of the second electrodes on theplurality of second protrusions, wherein an adjacent first protrusionand second protrusion form a pair of protrusions, wherein the firstprotrusion and the second protrusion in the pair do not overlap witheach other, or at least partially overlap with each other, and whereinthe plurality of sub-sensing regions comprise a first sub-sensing regionfor sensing a shear force in a first direction.
 23. The force sensor ofclaim 22, wherein the plurality of sub-sensing regions comprise a secondsub-sensing region for sensing a shear force in a second direction. 24.The force sensor of claim 22, wherein the plurality of sub-sensingregions further comprises: a second sub-sensing region configured tosense a shear force in a second direction, a third sub-sensing regionconfigured to sense a shear force in a third direction, and a fourthsub-sensing region configured to sense a shear force in a fourthdirection, and wherein the first, second, third and fourth directionsare on a same plane.
 25. The force sensor of claim 24, wherein thefirst, second, third and fourth directions comprise an upward direction,a downward direction, a leftward direction, and a rightward direction.26. The force sensor of claim 25, wherein the at least one sensing cellfurther comprises a pressure sensing region for sensing a pressure inthe thickness direction.
 27. The force sensor of claim 24, wherein thesecond sub-sensing region is disposed adjacent to the first sub-sensingregion in the first extending direction, wherein the third sub-sensingregion is disposed adjacent to the first sub-sensing region in thesecond extending direction, and wherein the fourth sub-sensing region isdisposed adjacent to the third sub-sensing region in the first extendingdirection.
 28. The force sensor of claim 27, wherein the firstsub-sensing region shares the same first electrode with the secondsub-sensing region, and wherein the third sub-sensing region shares thesame first electrode with the fourth sub-sensing region.
 29. The forcesensor of claim 28, wherein the first sub-sensing region shares the samesecond electrode with the third sub-sensing region, and wherein thesecond sub-sensing region shares the same second electrode with thefourth sub-sensing region.
 30. A force sensor, comprising: a firstsurface and a second surface facing each other in a first direction; afirst protrusion protruded from the first surface toward the secondsurface; a first electrode on the first protrusion; a first forcesensing layer on the first electrode; a second protrusion protruded fromthe second surface toward the first surface; and a second electrode onthe second protrusion, wherein the first protrusion and the secondprotrusion are not overlapped with each other or are partiallyoverlapped with each other, wherein the first protrusion does not comein contact with the second electrode in the first direction when theforce sensor is pressed in the first direction.